Nobuko Sasaki is a lecturer at a university in Tokyo. She is the Azure Apostle and former accomplice to the Azure King, her lover, and attempts to ruin the Armed Detective Agency after her lover's death. Sasaki is a young woman of slim build with pale skin and dark brown eyes. She has straight black hair that reaches her mid-back, and long bangs across her forehead brushed slightly to the right. She wears a pale, cream shirt under a white bolero, a knee-length, light grey skirt, black stockings, and black low heels. During her visit to the cemetery, and later her death, she wears a plain white kimono. While Sasaki initially seems a kind, friendly, and a rather patient woman, she is more than meets the eye. An accomplished woman in the criminology field, she's remarkably intelligent and skilled in her field of expertise, giving her an especially profound understanding of people. A resourceful woman, she succeeds in manipulating a number of infamous criminals from behind the scenes, leaving few tracks and no way for her victims to track her down. Having no friends or family to turn to, Sasaki devoted herself to the Azure King's ideology, admitting to having no strong ambitions of her own, instead of appearing to cling to her lover's instead. Consequently, when the Azure King contemplated suicide after failing to change the corrupted government from the inside, Sasaki shows a surprisingly ruthless, drastic side, being the one who arranged many of the Azure King's terrorist attacks. This further emphasises Sasaki's intelligence, manipulating the situation from the background and allowing her lover to 'fulfil' his ideals. She shared his belief that the law system is too flawed to give influential people their due punishments, and had no qualms with schemes that led to not only their deaths but countless other victims. To Sasaki, the end justified the means: punish the so-called 'nonpunishable'. For all her accomplishments and wit, Sasaki, ultimately, feels hollow inside since the death of her lover, the Azure King. Having devoted herself to another person's ideology, Sasaki essentially lost her reason for living after his demise. She exhausted herself in attempts to fulfil her lover's desires and sense of justice, which she herself acknowledges did nothing but hurt her in the end. With no one to truly blame, Sasaki directed her anger and grief towards the Armed Detective Agency, due to their involvement in the Azure King's death, as if she had no one to blame, she felt she'd lose her mind. Nonetheless, Sasaki feels no joy nor sense of accomplishment in severely damaging the Agency's reputation. During her confrontation with Doppo Kunikida and Osamu Dazai, she expresses nothing but a hollow, exhausted sensation, reaching the end of her ropes in trying to fulfil the Azure King's ideals, noting the man never said he loved her to begin with. Her targeting the Agency stems from both resentment and desperation for something to live for, unable to live for her own desires. The victims who suffered because of her she viewed only as a means to an end. Sasaki points out that she could never with an idealist, as she'd always come last compared to their ideals, and ultimately be left behind. To her, the idealism the Azure King and Kunikida shared inevitably led people like Sasaki to feel left behind, always put second to ideals that could never truly be reached. Ironically, it's that exact nature that drew her toward Kunikida, to the point where she attempted to confess her love to him in her dying moments, showing considerable conflicting emotions with her feelings towards idealists.